Process of hardening steel.



To' all whom, it may concern UNITED sTATns PATENT OFFICE.

kROBERT A. HADFIELD, or siliifiriviiinn, ENGLAND. l

PROCESS o F 'i v Application filed Tobi-nary l yBe it known that I, Rouna'r A. HADFIELD, a subject. ofthe King ol Great Britain, residing at Sheffield, countyof York,yEngl'and, have invented an Improvement in Processes of Hardening Steel, of Whiclrtlie following isa specification. 4

. In the resistance to coiiipre'ssion oilicred by a number ofdilierent kinds of hardlsteel vl have found by experiment that there are comparatively. small differences 'up to a certain load per square inch; but this dillerence changes greatly Whenthe conipressionis further increased. i j

.This 4invention has for its object theproduction of a method or process of treatr'nent for steelwhereby the resistance thereof to compression when subjected to considerable pressure is very greatly increased;

The steel to be treated, whether inl cast orA forged form, is heated, either directlyor after being annealedyin any desired manner to a temperature of not less than about 850 centigrade, and it may be up to from 1,000c cen-- 'tigrade-to 1,150 centigrade, depending upon the amount of carbon in the steel and the degree of hardness-or stiffness it' is desired to impart thereto, For'hard, steel containing, f

. say,.about 0.8 percent. carbon the steell is Specification` of Letters atent.

8,1903. senti No. 143,997.

HARM-:Nine STEEL.

. Patented Jan. 23, 1906.

harder steel the relient-ing may be carried to about 600 centigrade, whereas if a-touglicr steel is required the rclieating may he carrie'd up to about (580 ceiitigriide. l have found, however, that a tei'nperature'of about 7200 centigrade should not'be exceeded. asin such case the steel will become too softand lose its stiffness orresist'since to high conipression stress. 1n the relieating, therefore, temperatures above 720 centigrzidc should be avoided. l/Vhen only a partial cooling of the steel is eifected alter the preliminary heating, either in the furnace or the open air, the latter being preferred, thesteel is reliented after its teniperatureis lowered to from 300 centigrnde to 40()o centigrade. 'The final cooling after reheuting may be effected in any convenient manner-as,` for instance,

in one or other of the Ways hereinbefore men` v tioned for the cooling after preliminary heatingA. l

By'tlie process described steel can be obtained whose resistance to coinprossioii'is as high, if not higher, than that of Water-hardened steel,.but which is less brittle,fso that .by the, process described it is possible to obtain wi'thoutfincurring the stresses set u by Water-quenhing a. steel of great liardiiiess aand of greater strength than water-hardened 3o heated to ateinpereture ofnot less than 850 steel. The difficulty ofv waterquenching centigrade and it may be upward to la teniv steel is intensified-.by the fact'tliat it is not perature of from 975 centigrade to 1,000?? 4practicable to quenclrbeyoiid a certain teincentigrade, the harder the steel required' the perature, as steel liable to crack inhardhigher the temperature to which it is heated, ening when heated beyond freni 7809 to 850 3 5 the heating being conducted in any suitable ceiitigrade,according tothe size of the article, furnace; The heatedsteel-is then allowed to Whereas in conformity nth niy present incool down eithercompletelvtoabout the temvention there is no sudden cooling, and the peinture of theexter'nalairvoronlypartially- Steel can be heated io the high temperatures say to about 300" ceutigrade to 400' centi referred to .without damage.-

40 grade.' Thecooling in ay'lie effected in the' My inv'nt-ion is appliciiblcto steel of varis heatiiigfurnace, but preferably in `the open ous grades, the stilieziiugtemperatures being air1 whether the cooling be l('.onipleti'i or only higher tlielowcr thi. percentage ofcarbon. partial, and if it desired to 'secure greater The softiie'ss liereinbei ore referred to in vatoughness in the resultant` product conipieize rious steels pro'izi'blydue to the carbon pres- 45 cooling may be conducted in sand or other ent 'in the Steel being in the forni known as icc suitable non-conducting material. Ait Jhe Lcarbid carbon aud the steel while very preliminary heating vhtreinbeore described tough coni paintively weak in its resistance and the subsequent cooling the steel is reto high compression stresses. Y heated to a temperature of from about, 500" Bytreatinentoi the steelashereinheorede- 5o centigrade up to about 720 centigrade and scribed the carbon is transformed or changed 105 then allowed to cool. The harder the steel is again into the hardening forin to a greater or required tlic lower should be the rehearing less degree, according to the heating funnierternperature, and the tougher the steel is re aure employed. llie higher such' tenipei'- quired the higher should be the reheating ature the higher will be the ainoiuit other y 55 temperature. For example, to obtain a dening-carhon present und the hui'derwill be rio y the steel, and its resistance to compression stresses is thereby-increased. In treating steel containing about 0.8 per cent. carbon, referred to herein, the minimum is about So cent-igiadc and the maximum desirable teint My invention' is particul'irly adapted toy the treatment of hard steel for use in the 1 manufacture of armor-piercing projectiles to stillen them and increase their strength and resistance to coiripression; but. in v invention also applicable to the treatment of steel higher than 7120n centigradi', and liiiall slowly cooling the steel a'l'ter reheating.

'l`he method ot hardening steel, which eonsistsin raising-the temperatureol` t he steel to not less than n50c centigrade and not more than 1,1500 centigi'adc; permitting the steel t'o cool; reheating the cooled steel to a temperature not higher than 7120O centigrade, aml ininiediatel)Y thereafter permitting the steel to cool slowl)v from the reheating leiiipei'ature.

(l. The method ollv hardening steel which consists in raisingthe temperatureol1 the steel t above 01o centigrade, and below 1,150O centigrade, permitting it to cool slowl relientl ing the cooled steel toa temperature ol` or used l'or a varietyol" other purposes, such as niej the steel after such reheatiiig.A

shoes and dies for ore-crushing apparatus, the wearing parts ol" crushing machinery, rolls o1 various lginds, car-wheels, and cuttingtools ol' variousfltinds.

.Having .lescitibed my invention, what I clam, and desire to secure by Letters Patent,

to about 075'? centigrade; permittingl it to cool slowly; iebeatiiig the cooled steel to a temitcrature.of about 500 centigrade: and permitting,r the steel to cool slowly alter such reheating 2. '.lhe method of hardening steel and inipai'ting thereto high resistance to compression, which consists in raising the temperature ol' the steel to above S50O ccntigrade and .not over 1,150o centigrade; permitting it to cool slowly; reheating the cooled steel to a tempt-rat ure of or `over 080 centigrade, and 'permitting the steel to cool slowly immediatel v al'ter such reheating. v

3. 'lhe method of hardening,r steel and imparting theretohigh resistance to compression. which consists in raising the temperature ol' the steel to between 975 centigradd and 1.000 centigrade; permitting the steel to cool slowly: reheatiiig the cooled steel to a temperature of or over 500O centigriide, and slowly cooling the steel :il'ter such reheatmg. --l.- 'lhe method of hardeningr steel, which 1 consists in raisingthc temperature of the ysteel te above w00t-emigrado and not over 1,150o

`wiitigi'adc; permitting it to cool slowly to about the tciiiperatitre ol the external air; reheatmg the` .cooled steel toa temperature not over 500O centigrade, and linally slowly cooli. The method ol' hardening steel and imparting,r thereto high resistance to compression, which ,consists in raising the temperature of the steel to about .175D centigradc, permitting the steel to cool slowlv. reheating the cooled steel to a temperature ol' or over 680 ccntigrade and below 720O ccntigrade. and slowl \v cooling the steel l'rom such lastnamed temperature.

8. The ii'iethod of hardening steel, which consists iii raising the tcmnerat ureol' the steel from about S50O centigrade upward, aml not higher than 1,150o centigiade; cooling the steel to not niorc'tlian J100o centigrade; reheating the partially-cooleil steel to about 500O centligiade and upward, and liiiall)Y permitting the reheated steelto cool.

Q 'l`h'e*n;ethod ol' hardening steel which consists'n raisingr the temperature ol' the steel to from about Stlo'centigrade upward to butl not higher than 1,1500 centigrade, according lto the amount of carbon in the, steel; cooling the stceVslowly to not more thairlDOC' centigrade, relieating the cooled steel to a temperature of about 500 cen'tigrade and upward according to the hardness or toughness required; and iiinnediately and slowly cooling the reheated steel from the eheating temperature. l

ln testimony whereof I have. signed my naine to this-specification in the presence of -two subscribing,witnesses. t

` RQBEHT ,A. HADFIELD,

'BAIN L. CAMPBELL,

LUTHER J.\PARR.

ICO 

